man/standard-conf.xml

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   2 <!DOCTYPE refsection PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3           "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
   4
   5 <refsection>
   6   <refsection id='confd'>
   7     <title>Configuration Directories and Precedence</title>
   8
   9     <para>Configuration files are read from directories in
  10     <filename>/etc/</filename>, <filename>/run/</filename>, and
  11     <filename>/usr/lib/</filename>, in order of precedence.
  12     Each configuration file in these configuration directories shall be named in
  13     the style of <filename><replaceable>filename</replaceable>.conf</filename>.
  14     Files in <filename>/etc/</filename> override files with the same name in
  15     <filename>/run/</filename> and <filename>/usr/lib/</filename>. Files in
  16     <filename>/run/</filename> override files with the same name in
  17     <filename>/usr/lib/</filename>.</para>
  18
  19     <para>Packages should install their configuration files in
  20     <filename>/usr/lib/</filename>. Files in <filename>/etc/</filename> are
  21     reserved for the local administrator, who may use this logic to override the
  22     configuration files installed by vendor packages. All configuration files
  23     are sorted by their filename in lexicographic order, regardless of which of
  24     the directories they reside in. If multiple files specify the same option,
  25     the entry in the file with the lexicographically latest name will take
  26     precedence. It is recommended to prefix all filenames with a two-digit number
  27     and a dash, to simplify the ordering of the files.</para>
  28
  29     <para>If the administrator wants to disable a configuration file supplied by
  30     the vendor, the recommended way is to place a symlink to
  31     <filename>/dev/null</filename> in the configuration directory in
  32     <filename>/etc/</filename>, with the same filename as the vendor
  33     configuration file. If the vendor configuration file is included in
  34     the initrd image, the image has to be regenerated.</para>
  35
  36   </refsection>
  37
  38   <refsection id='main-conf'>
  39     <title>Configuration Directories and Precedence</title>
  40
  41     <para>The default configuration is defined during compilation, so a
  42     configuration file is only needed when it is necessary to deviate
  43     from those defaults. By default, the configuration file in
  44     <filename>/etc/systemd/</filename> contains commented out entries
  45     showing the defaults as a guide to the administrator. This file
  46     can be edited to create local overrides.
  47     </para>
  48
  49     <para>When packages need to customize the configuration, they can
  50     install configuration snippets in
  51     <filename>/usr/lib/systemd/*.conf.d/</filename>. Files in
  52     <filename>/etc/</filename> are reserved for the local
  53     administrator, who may use this logic to override the
  54     configuration files installed by vendor packages. The main
  55     configuration file is read before any of the configuration
  56     directories, and has the lowest precedence; entries in a file in
  57     any configuration directory override entries in the single
  58     configuration file. Files in the
  59     <filename>*.conf.d/</filename> configuration subdirectories
  60     are sorted by their filename in lexicographic order, regardless of
  61     which of the subdirectories they reside in. If multiple files
  62     specify the same option, the entry in the file with the
  63     lexicographically latest name takes precedence.  It is recommended
  64     to prefix all filenames in those subdirectories with a two-digit
  65     number and a dash, to simplify the ordering of the files.</para>
  66
  67     <para>To disable a configuration file supplied by the vendor, the
  68     recommended way is to place a symlink to
  69     <filename>/dev/null</filename> in the configuration directory in
  70     <filename>/etc/</filename>, with the same filename as the vendor
  71     configuration file.</para>
  72   </refsection>
  73 </refsection>